Heritage of Innovation

World War I, and the interest in the airplane as a weapon, delayed the early helicopter’s development. After the war, the "autogyro" was invented by De la Cierva (Spain). Pitcairn (USA), Kellett (USA), the autogyro company of Great Britain, and Focke (Germany) all produced variations of this aircraft. Its unpowered, wind-turned rotor made the autogyro capable of slow flight, free of stalling, but without the capability of hovering.

The helicopter, with a powered rotor, promised hovering but had greater technical problems. These early machines were not developed to the point of practical use. Many experts, including the Wright brothers, deemed the helicopter too complicated. Despite the skepticism usually met by any new idea, a handful of designers were determined to make VTOL (Vertical Take-Off or Landing) technology work.

Breguet successfully flew his second helicopter (two co-axial rotors) over a 9 km. closed course. De Bothezat’s (Russia/USA) four rotor helicopter flew in 1922, but the pilot declared it deficient in control. Berliner, Hafner, Young, Wilford, Daland, Lepage, and others developed various methods of controlling VTOL. In 1939 Igor Sikorsky flew his VS-300, the first successful helicopter in the United States.

In 1936, Frank N. Piasecki and a group of engineering students from the University of Pennsylvania formed the P-V Engineering Forum to design and build their own helicopter. The story of the resulting projects and achievements follows.

Vertical air lift began in 1783 with a hot air balloon made by the Montgolfier Brothers of France. One hundred and twenty years later at Kitty Hawk, N.C., the Wright Brothers flew the first successful powered airplane. Four years later, Louis Breguet of Paris built the first helicopter to lift a man. The growth of aeronautical technology gave birth to a major industry responsible for many world wide social, political, and economic changes.

The following pages show the story of the efforts and accomplishments of the Piasecki team in vertical air lift technology. Shown are the aircraft they designed, developed, produced, and successfully flew over fifty five years of innovation and evolution.

The achievements which mark Piasecki vertical lift aircraft designs, and some visions of the future, are presented for the interest of those whose opinions are valued, and as a tribute to those who made these accomplishments possible.

In the mid 1950's, Piasecki Helicopter Corporation had a greater backlog than all other helicopter companies in the free world combined. Because of the rapid success of the company, and the need for large capital inputs, many mergers were considered and investigated. Finally, the company was sold to the Boeing Airplane Company.

In 1955, Frank Piasecki and members of his original team left Piasecki Helicopter Corporation and started Piasecki Aircraft Corporation (PiAC) to work on new VTOL aircraft concepts.

PiAC’s design philosophy concentrated on advanced VTOL aircraft configurations, continuing the exploratory work that previously had been done throughout earlier helicopter development. Heavier lift and higher speeds were the two major performance goals.

Initially, heavy lift VTOL studies were performed for the army including the movement of a 50 ton tank externally, a matrix of rotor/propulsion systems studies showed multiple shaft driven rotors were the optimum heavy lift configuration for the near-term and a blade mounted turbo-jet system (PA-1) for the long term. The high development cost of the latter unfortunately dissuaded any further research effort.

By the mid 1950's, higher speeds were of growing interest to the USMC for forward battle areas. A design study, wind tunnel tests, and full scale component tests were made for the bureau of aeronautics for a VTOL configuration utilizing a vectored flow ducted propeller in which the duct was of sufficient chord to provide the required wing area. A large instrumented test stand was built with a 1,200 hp piston engine for ducted propeller research.